Study and simulation of the unified power flow controller effect on power systems

The main objectives of flexible AC transmission systems (FACTS) are to increase the transmission capacity of lines and to control the power flow over designated transmission system. FACTS can perform all objectives of reactive power control and voltage control within the transmission and distribution networks and at load terminals. Several schemes of flexible AC transmission systems FACTS are either in use today. One of the most important FACTS devices is the Unified Power Flow Controller (UPFC), which is used to investigate its effect on load flow and loss reduction in power system. The UPFC is a combination of a static shunt synchronous series compensator (STATCOM) and a static synchronous series compensator (SSSC), which are coupled via a common DC link. The UPFC is a device, which can control simultaneously all the three parameters of line power flow which are line impedance, voltage and phase angle. The UPFC improves terminal voltage regulation, series capacitor compensation and transmission angle regulation. The main objectives of this work are to develop a new basic control scheme and comprehensive analysis for a unified power flow controller (UPFC) also to develop MATLAB program which simulate the UPFC and its action on the power system. This developed technique showed to be very effective and it will enable engineers to study and investigate how the UPFC can affect the transmission system using the series voltage and shunt current injection. It was possible to demonstrate that the UPFC can improve the system characteristics and gives the best transient and dynamic stability. It can highly improves the power factor. Many cases are investigated and studied such as application of the UPFC to control voltage and power flow. The cases are tested for the same simulated power system but with different load types and different system voltages. In all cases, the performance of the system was analyzed, tested and studied to indicate voltages, currents and power perfo- rmance and showed to be satisfactory.